The present disclosure relates generally to battery monitoring systems and, more particularly, to an integrated battery monitoring device and system having distributed, self-powered sensors.
Conventional battery installations commonly utilize a plurality of series connected battery cells in order to generate operating voltages higher than the nominal 1-3 volts typically present in an individual battery cell. In certain applications, a sufficient number of cells can be connected to achieve voltages as high as 400 volts (V) or more. Collectively, these multiple, series connected battery cells are referred to as a battery string. As a battery string is being charged, the individual cells could react differently to the charging current. In particular, it is desired that a given cell not be overcharged since this could damage the cell and perhaps even the entire battery.
Accordingly, battery monitoring systems are sometimes used to periodically monitor the condition of the battery string by measuring the voltage, resistance, and temperature of the battery string and the individual cells This type of battery monitor system generally works in tandem with a battery charging system by providing battery information to the charging system, in order to maintain a proper state of charge and to regulate the voltage in the battery string. Alarms in the battery monitor system may be enabled or annunciated whenever a measured battery parameter exceeds a specified value so as to alert an owner/operator that the battery system is outside its designed operating range. In addition, a monitoring/charging system may also be used to periodically partially discharge or charge the battery string and/or individual battery cells by selectively coupling a test load or voltage source across the battery string or individual cells.
However, conventional battery monitoring systems tend to be “wiring intensive” in that each measurement point (e.g., a voltage or temperature sensor device for a given cell) generally requires at least two signal leads and two power leads for each parameter measured. In addition, if the system is provided with the capability of switching in a load for discharging a given battery cell, the amount of wiring is further increased. This is especially the case for battery strings having hundreds of individual cells. Furthermore, since the common mode voltage of an individual battery cell can be on the order of hundreds of volts with respect to ground, some form of voltage isolation is needed between the measuring device and the system controller. This in turn results in the use of a local, isolated power source associated with the measuring device. Thus, it is desirable to be able to implement a battery monitoring system that is less wiring intensive and that utilizes fewer components, thereby increasing simplicity and reducing costs.